The lecture time is 36 hours and 55 minutes, so it is scary when you first watch the lecture. I also felt resistance when I first learned this part... However, the true value of this lecture is the part where the internal operation principles are explained in detail through the debugger. As you follow the lecture to dig into the detailed operation principles through the debugger, you will learn how to use the debugger yourself, which was a great help in improving your development skills. If you follow this lecture at the stage where you have gone through the Spring introductory stage (learning core, web, jpa, boot, etc.) and learn the internal automatic settings and operation flow through the debugger, you will feel that your understanding of security will grow rapidly. And as of now, most of the security-related materials are based on deprecated or unused materials, but this lecture was created with version 6 and later in mind. It is hard to find lectures or materials that explain security, or even specific technologies, in such depth. This is a lecture that I really recommend.